Message sent from holiday job by Joker, perhaps (8)
I believe the answer is:
postcard
'message sent from holiday' is the definition.
'job by joker perhaps' is the wordplay.
'job' becomes 'post' (post is a kind of job).
'by' says to put letters next to each other.
'joker perhaps' becomes 'card' (a joker is a type of playing card).
'post'+'card'='POSTCARD'
(Other definitions for postcard that I've seen before include "Holiday missive" , "Limited communication" , "Brief message" , "It's sent without an envelope" , "Holiday communication" .)